At least two people have been killed in a car bomb blast at a market in a rebel-held suburb of the Syrian capital, as residents shopped a day before the start of the holy month of Ramadan, activists said.

The blast on Saturday in Douma wounded dozens of others, according to the UK-based Syrian Observatory for Human Rights and videos released by activists in the area.

The activists said the market was crowded a day before Ramadan, when observant Muslims fast from dawn to dusk and feast in the evenings.

Other footage uploaded to the internet showed the flaming wreckage of an overturned vehicle in front of the blackened pillars of a nearby building.

Abu Yazan, an activist in the nearby suburb of Saqba, told the AP news agency via Skype that hospitals were full of wounded people.

Other videos posted online showed the bloodied and burnt bodies of two dead boys. Other people, including children, were seen receiving treatment. Several other wounded people lay sprawled out on bloodstained white tiles.

Douma, one of the most populous suburbs of Damascus, has been under rebel control for more than two years.

The observatory and Abu Yazan said the Islamic State of Iraq and the Levant was believed to be behind the blast, because of a rivalry with other rebel groups in the area.

The ISIL has been fighting against rival rebel factions, including al-Qaeda's official affiliate, the Nusra Front, since January in battles that have left more than 6,000 people dead, according to the observatory.

The observatory says that more than 160,000 people have been killed in Syria since March 2011, although that figure cannot be independently verified. The UN stopped counting at 100,000.

The number of refugees are also expected to hit 4.1 million at the end of 2014.